Alsbury, 39, was an experienced flier who co-piloted the same craft when it first broke the sound barrier last year. He worked for Scaled Composites — which built and operates SpaceShipTwo — for more than a decade, according to his biography.

Another pilot aboard the ship, Peter Siebold, parachuted to safety but was also seriously injured, authorities said. He was to undergo surgery Saturday afternoon, according to the Kern County (Calif.) Sheriff's Office.

Alsbury held the titles of project engineer and test pilot, and was also sitting in the co-pilot's seat when the craft was first dropped in 2010 from its carrier aircraft several miles above the Earth for an unpowered glide test. According to test logs, Alsbury flew primarily as the craft's co-pilot, logging at least seven trips from 2010 to early 2014.

His identity was confirmed to the Los Angeles Times by the Kern County (Calif.) Coroner's Office and to the Associated Press by Kern County Sheriff Donny Youngblood. The Daily Mail reported that Alsbury was a married father of two. Records show he lived in Tehachapi, Calif., near the Mojave Air and Space Port, where the test flights were conducted.

Saturday morning, two men intercepted reporters in front of Alsbury's modest two-story house to say that the family is grieving and had no comment at this time. One neighbor who declined to identify himself said he believed the family had lived in the neighborhood about two years and had young children.

A coworker, Clint Nichols, described Alsbury as "the great pilot, a great engineer."

Alsbury was one of only a small handful of men who had ever flown the spaceship and its companion aircraft.

Scaled Composites employs multiple test pilots who trade off duties. Alsbury had also been co-pilot on WhiteKnightTwo, which carried the separate spaceship high above the ground before it was dropped to begin rocket-powered flight.

Alsbury's official bio says he held a B.S. in Aeronautical Engineering from California Polytechnic State University-San Luis Obispo and was a member of the Society of Experimental Test Pilots and Society of Flight Test Engineers. The undated bio said he had 15 years and more than 1,800 hours of flight experience, and held his single and multiengine instrument commercial, glider commercial and single and multiengine instrument flight instructor certificates.

Authorities have not yet said whether Alsbury or Siebold was commanding the craft when it exploded, but Siebold typically flew as a pilot and Absbury flew as co-pilot, according to company flight logs.

Virgin Galactic last year hired former astronaut Frederick Sturcklow and a longtime American fighter and test pilot Michael Masucci to beef up its corps of pilots as it completed testing and prepared for commercial spaceflights.

Billionaire Virgin Galactic founder Richard Branson salutes the bravery of test pilots, and vows to find out what caused the crash of his prototype space tourism rocket that killed one crew member and injured another during a news conference in Mojave, Calif. Brian Melley, AP

An image from video shot by KABC TV in Los Angeles shows wreckage of what is believed to be SpaceShipTwo in California's Mojave Desert. The space tourism rocket exploded during a test flight. KABC TV via AP

ORG XMIT: NY124 In this photo released by Virgin Galactic, the Virgin Galactic SpaceShipTwo, or VSS Enterprise, glides toward the earth on its first test flight after release from the mothership, WhiteKnight2, also known as VMS Eve, over the Mojave, Calif., area early Sunday, Oct. 10, 2010. SpaceShipTwo is undergoing rigorous testing before it can carry tourists to space. In the latest test, SpaceShipTwo did not fire its rocket engine to climb to space. The craft was piloted by engineer and test pilot Pete Siebold from Scaled Composites. (AP Photo/Clay Observatory for Virgina Galactic, Mark Greenberg) NO SALES Mark Greenberg, Virgin Galactic, via AP

(FILES) This January 23, 2008 file photo shows Sir Richard Branson, founder of Virgin Galactic, poses with a model of the SpaceShipTwo on Jan. 23, 2008, at the America Museum of Natural History in New York. Stan Honda, AFP/Getty Images